Optical filter and process for producing the same

ABSTRACT

The optical filter of the present invention is provided with a near infrared light absorption layer that contains a component composed of copper ions and a phosphoric ester compound expressed by the following Formula (10), in which the phosphorus atom content in the near infrared light absorption layer is 0.4 to 1.3 mol per mole of copper ions, and the copper ion content in the near infrared light absorption layer is 2 to 60 wt %. Thus keeping the phosphorus atom and copper ion content within specific ranges results in good near infrared light absorption and in improved moisture resistance whereby devitrification caused by whitening is suppressed

TECHNICAL FIELD

This invention relates to an optical filter and a method formanufacturing the same.

BACKGROUND ART

Conventional optical filters having near infrared light absorptioncharacteristics have been disclosed in Japanese Laid-Open PatentApplication H6-118228 and elsewhere, in which the optical filtercontains a phosphoric ester compound and an ionic metal component whosemain component is copper ions.

A characteristic of this optical filter is that it efficiently absorbsnear infrared light, but has high transmissivity to visible light, andis therefore used in applications that require the transmission ofvisible light and the blocking of near infrared light, such as thermalabsorption members for windows, visibility correction filters, anddisplay panels.

DISCLOSURE OF THE INVENTION

In terms of raising the visible light transmissivity of an opticalfilter, and from the standpoints of ease of handling and less bulkiness,it is useful for the optical filter to be thinner. Copper ions are whatprovide the near infrared light absorption, and the copper ion content(concentration) must be sufficiently high in order to obtain an opticalfilter having adequate near infrared light absorption when the thicknessthereof has been reduced.

The inventors studied the above-mentioned conventional optical filters,and discovered that the environment resistance of these conventionaloptical filters tends to deteriorate when the copper ion content israised.

In specific terms, moisture (water) in the environment has the effect ofgradually whitening (clouding) an optical filter over long-term use,until so much transmissivity is lost that visible light can no longer betransmitted (known as devitrification). In particular, thisdevitrification tends to accelerate in environments or seasons of hightemperature and humidity, and this can shorten the service life of anoptical filter.

The present invention was conceived in light of this situation, and itis an object thereof to provide an optical filter that has adequate nearinfrared light absorption while also having outstanding moistureresistance.

The inventors conducted diligent research aimed at achieving the statedobject, and arrived at the present invention upon discovering that inthe composition of an optical filter containing a phosphoric estercompound and a copper compound, or copper phosphate compound, the ratioin which the phosphorus atoms and copper ions are contained greatlyaffects the moisture resistance of the optical filter. Specifically, theoptical filter of the present invention comprises a near infrared lightabsorption layer containing the following component A and/or thefollowing component B:

Component A: a component composed of copper ions and a phosphoric estercompound expressed by the following Formula (1),

Component B: a copper phosphate compound obtained by reaction of acopper compound with the phosphoric ester compound,

wherein the phosphorus atom content in the near infrared lightabsorption layer is 0.4 to 1.3 mol per mole of copper ions, and thecopper ion content in the near infrared light absorption layer is 2 to60 wt %, and preferably 2 to 20 wt %, with 2 to 15 wt % beingparticularly favorable.

In Formula (1), R is a group expressed by the following Formula (2),(3), (4), (5), (6), (7), (8), or (9), an alkyl group, an aryl group, anaralkyl group, or an alkenyl group, n is 1 or 2, and when n is 1, the Rgroups may be the same or different.

In Formulas (2) to (9), R¹¹ to R¹⁷ are C₁ to C₂₀ (number of carbonatoms) alkyl groups or C₆ to C₂₀ aryl groups or aralkyl groups (wherethe one or more hydrogen atoms bonded to the carbon atoms that make uparomatic rings may be substituted with C₁ to C₆ alkyl groups orhalogens), R²¹ to R²⁵ are hydrogen atoms or C₁ to C₄ alkyl groups (whereR²³, R²⁴, and R²⁵ cannot all be hydrogen atoms), R³¹ and R³² are C₁ toC₆ alkylene groups, R⁴¹ is a C₁ to C₁₀ alkylene group, R⁵¹ and R⁵² areC₁ to C₂₀ alkyl groups, R⁶¹ is a hydrogen atom or methyl group, m is aninteger from 1 to 6, k is an integer from 0 to 5, p is an integer from 2to 97, and r is an integer from 1 to 4.

In this optical filter, the phosphoric acid groups of the phosphoricester compound are bonded to the copper ions by coordination bondingand/or ion bonding, these copper ions are dissolved or dispersed in thenear infrared light absorption layer in a state in which they aresurrounded by the phosphoric ester, and near infrared light isselectively absorbed through electronic transition between the d orbitsof these copper ions.

It has been confirmed that from the standpoint of the dispersibility ofcopper ions in the near infrared light absorption layer, and themoisture resistance of the optical filter, it is extremely favorable forthe phosphorus atom content in the near infrared light absorption layerto be 0.4 to 1.3 mol per mole of copper ions, that is, for the ratio inwhich the phosphorus atoms are contained versus the copper ions(hereinafter referred to as “P/Cu”) to be 0.4 to 1.3.

If the P/Cu molar ratio is less than 0.4, there will be an excess ofcopper ions coordinated with respect to the phosphoric ester compound,and the copper ions will tend not to disperse uniformly in the nearinfrared light absorption layer. The near infrared light absorptionlayer may also be formed from a resin composition in which theabove-mentioned component A and/or component B is contained in a resin.This will allow the characteristics of the resin to be imparted to theoptical filter, and here again, if the molar ratio of P/Cu is less than0.4, the copper ions will tend not to disperse uniformly in the resin.On the other hand, if the P/Cu molar ratio is over 1.3, devitrificationwill tend to occur more readily when the thickness of the optical filteris reduced and the copper ion content raised, and this tendency will beparticularly pronounced in environments of high humidity andtemperature.

It is preferable for the P/Cu molar ratio to be 0.8 to 1.3. Thedispersibility of the copper ions in the resin can be reliably andsufficiently raised if this molar ratio is at least 0.8.

Also, if the copper ion content in the near infrared light absorptionlayer is under the above-mentioned lower limit, it will tend to bedifficult to obtain adequate near infrared light absorption when thethickness of the optical filter or near infrared light absorption layeris reduced to about 1 mm. On the other hand, if the copper ion contentexceeds the upper limit given above, it will tend to be difficult todisperse the copper ions in the near infrared light absorption layer.The same tendencies are exhibited when, as mentioned above, the nearinfrared light absorption layer is formed from a resin compositioncontaining the above-mentioned component A and/or component B.

It is preferable for the phosphoric ester compound to be such that R⁶¹in Formula (9) is a methyl group, p in Formula (9) is 2 or 3, and r inFormula (9) is 1, or more specifically, for it to be a phosphoric estercompound expressed by the following Formula (10), or a phosphoric estercompound expressed by the following Formula (11).

If the alkylene oxide group in the methacryloyloxyalkyl group expressedby Formula (9) is thus an ethylene oxide group or propylene oxide group,the near infrared light absorption will be higher than with a phosphoricester compound having an alkylene oxide group in which theabove-mentioned p is 4 or greater. It is therefore possible to raise theselective absorption of near infrared light of the optical filter, andto raise its selective transmission of visible light.

If r (the repeat number of these alkylene oxide groups) is 1, there willbe substantially no deterioration in the visible light transmissivity ofthe optical filter overtime. Thus, the improvement in the moistureresistance of the optical filter will be even better. In contrast, withan optical filter in which r is 2 or greater, and especially one inwhich the number of alkylene oxide groups is an integer over 4, therewill be a tendency for moisture resistance, rigidity, heat resistance,and so forth to deteriorate more readily over time.

The method of the present invention for manufacturing an optical filteris a method for manufacturing an optical filter having a near infraredlight absorption layer containing the above-mentioned component A and/orcomponent B, and comprises the step of mixing or bringing into contact aphosphoric ester compound expressed by Formula (1), a copper salt, andwater.

In other words, this method comprises a step in which water is made tobe present when a phosphoric ester compound expressed by Formula (1) ismixed or brought into contact with a copper salt. This step isparticularly favorable when the copper salt is copper acetate, copperacetate monohydrate, copper benzoate, or another such copper saltanhydride or hydrate of an organic acid.

This affords better stability of the monomer composition in thepreparation of a resin composition by adding component A and/orcomponent B to a resin, for instance. An advantage of this is that itraises the transparency of the polymer (near infrared light absorptionlayer of the optical filter) obtained by polymerizing the monomercomposition.

It is favorable if a phosphoric ester compound expressed by Formula (1),a copper salt, and water are mixed or brought into contact such that thephosphorus atom content in the near infrared light absorption layer is0.4 to 1.3 mol per mole of copper ions, and the copper ion content inthe near infrared light absorption layer is 2 to 60 wt %.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross section illustrating an example of adisplay panel in which the optical filter of the present invention isused;

FIG. 1B is an exploded oblique view illustrating the layered structureof the display panel shown in FIG. 1A;

FIG. 2 is a perspective view illustrating an example of how the displaypanel in FIG. 1 is used;

FIG. 3 is a graph of the spectral transmittance spectrum of the opticalfilter in Example 1;

FIG. 4 is a graph of the spectral transmittance spectrum of the opticalfilter in Example 2;

FIG. 5 is a graph of the spectral transmittance spectrum of the opticalfilter in Comparative Example 1;

FIG. 6 is a graph of the spectral transmittance spectrum of the opticalfilter in Comparative Example 2; and

FIG. 7 is a graph of the spectral transmittance spectrum of the opticalfilter in Comparative Example 3.

BEST MODES FOR CARRYING OUT THE INVENTION

The optical filter of the present invention will now be described indetail.

The optical filter of the present invention comprises a near infraredlight absorption layer containing the above-mentioned component A and/orcomponent B. First, components A and B that make up the near infraredlight absorption layer will be described.

Component A

Component A is composed of copper ions and a phosphoric ester compoundexpressed by Formula (1) given above. Specific examples of the coppersalt used to supply the copper ions include copper acetate, copperacetate monohydrate, copper formate, copper stearate, copper benzoate,copper ethylacetoacetate, copper pyrophosphate, copper naphtenate,copper citrate, and other such copper salt anhydrides and hydrates oforganic acids, as well as copper hydroxide, copper chloride, coppersulfate, copper nitrate, basic copper carbonate, and other such coppersalt anhydrides and hydrates of inorganic acids.

Of these, copper acetate, copper acetate monohydrate, copper benzoate,copper hydroxide, and basic copper carbonate can be used to particularadvantage. Component A may contain other metal ions besides copper ions(hereinafter referred to as “other metal ions”), and examples of othermetal ions include ions from metals such as sodium, potassium, calcium,iron, manganese, magnesium, and nickel.

The above-mentioned phosphoric ester compound is manufactured by any ofthe following first, second, and third methods, for example.

First Method

This first method involves reacting phosphorus pentoxide with a compoundexpressed by the following Formula (12) in a suitable organic solvent(or without a solvent)

In Formula (12), R is a group expressed by the above-mentioned Formula(2), (3), (4), (5), (6), (7), (8), or (9), an alkyl group, an arylgroup, an aralkyl group, or an alkenyl group. Specifically, an alcohol,alkyl alcohol, phenol, etc., expressed by the following Formula (13),(14), (15), (16), (17), (18), (19), or (20) can be used favorably as thecompound expressed by the above Formula (12).

In Formulas (13) to (20), R¹¹ to R¹⁷ are C_(1 to C) ₂₀ alkyl groups orC₆ to C₂₀ aryl groups or aralkyl groups (where the one or more hydrogenatoms bonded to the carbon atoms that make up aromatic rings may besubstituted with C₁ to C₆ alkyl groups or halogens), R²¹ to R²⁵ arehydrogen atoms or C₁ to C₄ alkyl groups (where R²³, R²⁴, and R²⁵ cannotall be hydrogen atoms), R³¹ and R³² are C₁ to C₆ alkylene groups, R⁴¹ isa C₁ to C₁₀ alkylene group, R⁵¹ and R⁵² are C₁ to C₂₀ alkyl groups, R⁶¹is a hydrogen atom or methyl group, m is an integer from 1 to 6, k is aninteger from 0 to 5, p is an integer from 2 to 97, and r is an integerfrom 1 to 4.

Of the compounds expressed by Formula (12), specific favorable examplesof the alcohols expressed by Formula (13) that have aryl groups oraralkyl groups include the alcohols expressed by the following Formulas(21) and (22). Specific favorable examples of the alcohols expressed byFormula (15) that have aryl groups include the alcohols expressed by thefollowing Formula (23). Specific favorable examples of the alcoholsexpressed by Formula (17) include the alcohols expressed by thefollowing Formula (24).

As mentioned above, phenol is included among the compounds expressed byFormula (12), but in the present invention, the compounds expressed byFormula (12) will hereinafter be collectively referred to as “designatedalcohols” for the sake of convenience.

The organic solvent used in the reaction between the designated alcoholand the phosphorus pentoxide is one that will not react with phosphoruspentoxide, examples of which include hexane, cyclohexane, heptane,octane, benzene, toluene, xylene, petroleum spirits, and other suchhydrocarbon solvents; chloroform, carbon tetrachloride, dichloroethane,chlorobenzene, and other such halogenated hydrocarbon solvents; diethylether, diisopropyl ether, dibutyl ether, tetrahydrofuran, and other suchether solvents; and acetone, methyl ethyl ketone, dibutyl ketone, andother such ketone solvents. Of these, toluene and xylene are preferred.

In this “first method,” the reaction conditions for the designatedalcohol and the phosphorus pentoxide include a reaction temperature of 0to 100° C., and preferably 40 to 80° C., and a reaction temperature of 1to 24 hours, and preferably 4 to 9 hours, when the designated alcohol isan alcohol expressed by any of Formulas (13) to (20) (excepting thosehaving aromatic rings).

If the designated alcohol is phenol or one of the alcohols expressed byFormulas (13) to (17) that have an aromatic ring, the reactiontemperature is 0 to 100° C., and preferably 40 to 80° C., and thereaction time is 1 to 96 hours, and preferably 4 to 72 hours.

Also, in this first method, if the designated alcohol and the phosphoruspentoxide are used in a molar ratio of 3:1, for instance, the resultingcompound will be an approximately 1:1 mixture of a phosphoric monoestercompound in which the number of hydroxyl groups in Formula (1) is 2 (n=2in Formula (1)) (hereinafter referred to as a “monoester”) and aphosphoric diester compound in which the number of hydroxyl groups inFormula (1) is 1 (n=1 in Formula (1)) (hereinafter referred to as a“diester”). The reaction conditions and the proportions of thedesignated alcohol and phosphorus pentoxide can also be selected asneeded so as to adjust the molar ratio of monoester to diester to arange of 99:1 to 40:60.

Second Method

This second method involves reacting a designated alcohol with aphosphorus oxyhalide in a suitable organic solvent (or without asolvent), and hydrolyzing the product thus obtained by adding water. Thephosphorus oxyhalide is preferably phosphorus oxychloride or phosphorusoxybromide, with phosphorus oxychloride being particularly favorable.

The organic solvent used in the reaction between the designated alcoholand the phosphorus oxyhalide is one that will not react with aphosphorus oxyhalide, examples of which include hexane, cyclohexane,heptane, octane, benzene, toluene, xylene, petroleum spirits, and othersuch hydrocarbon solvents; chloroform, carbon tetrachloride,dichloroethane, chlorobenzene, and other such halogenated hydrocarbonsolvents; and diethyl ether, diisopropyl ether, dibutyl ether, and othersuch ether solvents. Of these, toluene and xylene are preferred.

The reaction conditions for the designated alcohol and the phosphorusoxyhalide include a reaction temperature of 0 to 110° C., and preferably40 to 80° C., and a reaction temperature of 1 to 20 hours, andpreferably 2 to 8 hours. Also, a monoester can be obtained in thissecond method by using the designated alcohol and the phosphorusoxyhalide in a molar ratio of 1:1.

When a designated alcohol expressed by Formula (14), (16), (17) (whenR²³ is a hydrogen atom), (18), or (20) is used, in addition to selectingthe reaction conditions and the proportions of the designated alcoholand phosphorus oxyhalide, it is favorable to use a reaction catalyst,such as titanium tetrachloride (TiCl₄), magnesium chloride (MgCl₂),aluminum chloride (AlCl₃), or another such Lewis acid catalyst, and acatcher for by-product hydrochloric acid, such as triethylamine,tributylamine, or another such amine, or pyridine.

A mixture of a monoester and a diester can be obtained by using theabove-mentioned reaction catalyst and hydrochloric acid catcher. Theconditions pertaining to the reaction, including the reaction catalystand the proportions of the designated alcohol and phosphorus oxyhalide,can also be selected as needed so as to adjust the molar ratio ofmonoester to diester to a range of 99:1 to 1:99.

When a designated alcohol expressed by Formula (13), (15), (17) (whenR²³ is an alkyl group), or (19) is used, the reaction conditions and theproportions of the designated alcohol and phosphorus oxyhalide areselected, and a Lewis acid catalyst and a hydrochloric acid catcher areused so as to obtain a mixture of a monoester and a diester, in whichcase the molar ratio thereof is adjusted to between 99:1 and 1:99.

If the designated alcohol is one with a small number m of repeatingunits of the alkylene oxide groups, the resulting phosphoric estercompound will be water soluble, so if an amine or other hydrochloricacid catcher is used, it will tend to be difficult to remove theresulting amine hydrochloride by washing with water. The amount in whichthe above-mentioned reaction catalyst is used is 0.005 to 0.2 mol, andpreferably 0.01 to 0.05 mol, per mole of phosphorus oxyhalide.

Third Method

This third method involves reacting a designated alcohol with aphosphorus trihalide in a suitable organic solvent (or without asolvent) to synthesize a phosphonic ester compound, and then oxidizingthe resulting phosphonic ester compound. The phosphorus trihalide ispreferably phosphorus trichloride or phosphorus tribromide, withphosphorus trichloride being particularly favorable.

The organic solvent used in the reaction between the designated alcoholand the phosphorus trihalide is one that will not react with aphosphorus trihalide, examples of which include hexane, cyclohexane,heptane, octane, benzene, toluene, xylene, petroleum spirits, and othersuch hydrocarbon solvents; chloroform, carbon tetrachloride,dichloroethane, chlorobenzene, and other such halogenated hydrocarbonsolvents; and diethyl ether, diisopropyl ether, dibutyl ether, and othersuch ether solvents. Of these, hexane and heptane are preferred.

The reaction conditions for the designated alcohol and the phosphorustrihalide include a reaction temperature of 0 to 90° C., and preferably40 to 75° C., and a reaction temperature of 1 to 10 hours, andpreferably 2 to 5 hours.

The means for oxidizing the phosphonic ester compound can be tosynthesize a phosphorohalidate compound, and then hydrolyze thisphosphorohalidate compound. The reaction temperature of the phosphonicester compound and the halogen here should be 0 to 40° C., andpreferably 5 to 25° C.

This phosphonic ester compound may also be refined by distilling priorto being oxidized. In this third method, a diester of high purity can beobtained, for example, by using the designated alcohol and thephosphorus trihalide in a molar ratio of 3:1. A mixture of a monoesterand a diester can be obtained by selecting the reaction conditions andthe proportions of the designated alcohol and phosphorus trihalide, inwhich case the molar ratio is adjusted to between 99:1 and 1:99.

Specific examples of the first phosphoric ester compound obtained withthe first to third methods given above include compounds expressed bythe following Formula (25)-a, the following Formula (25)-b, thefollowing Formulas (26)-a to (26)-x, the following Formulas (27)-a to(27)-x, the following Formulas (28)-a to (28)-v, and the followingFormulas (29)-a to (29)-n.

These phosphoric ester compounds can be used singly or in combinationsof two or more types, and from the standpoint of near infrared lightabsorption characteristics in copper compounds thereof, phosphoric estercompounds expressed by Formula (25)-b, Formulas (27)-a to (27)-x,Formulas (28)-a to (28)-v, and Formulas (29)-a to (29)-n are preferable,with the phosphoric ester compounds expressed by Formulas (28)-s to(28)-v being particularly favorable.

Component B

Component B is composed of a copper phosphate compound obtained througha reaction between the above-mentioned phosphoric ester compound and acopper compound. The copper salts discussed above can be used as thecopper compound, and the reaction between the above-mentioned phosphoricester compound (hereinafter referred to as the “designated phosphoricester compound”) and the copper salt can be conducted by bringing thetwo components into contact under the appropriate conditions. Morespecifically, the following methods (i), (ii), and (iii) can be used,for example.

(i) A method in which the designated phosphoric ester compound and thecopper salt are mixed and reacted.

(ii) A method in which the designated phosphoric ester compound and thecopper salt are reacted in a suitable organic solvent.

(iii) A method in which an organic solvent layer comprising thedesignated phosphoric ester compound contained in an organic solvent isbrought into contact with an aqueous layer in which a copper salt isdissolved or dispersed, thereby reacting the designated phosphoric estercompound and the copper salt.

The reaction conditions for this designated phosphoric ester compoundand the copper salt include a reaction temperature of 0 to 150° C., andpreferably 20 to 120° C., and a reaction time of 0.5 to 15 hours, andpreferably 1 to 10 hours, with 1 to 7 hours being even better.

There are no particular restrictions on the organic solvent used in theabove-mentioned method (ii) as long as it allows the dissolution ordispersion of the designated phosphoric ester compound being used, butexamples include benzene, toluene, xylene, and other aromatic compounds;methyl alcohol, ethyl alcohol, isopropyl alcohol, and other alcohols;methyl cellosolve, ethyl cellosolve, and other glycol ethers; diethylether, diisopropyl ether, dibutyl ether, and other ethers; acetone,methyl ethyl ketone, and other ketones; ethyl acetate and other esters;and hexane, kerosene, and petroleum ether.

It is also possible to use a polymerizable organic solvent such as a(meth)acrylate or other (meth)acrylic ester, styrene, α-methylstyrene,or another such aromatic vinyl compound.

Meanwhile, there are no particular restrictions on the organic solventused in the above-mentioned method (iii) as long as it is insoluble ordissolves poorly in water, and allows the dissolution or dispersion ofthe designated phosphoric ester compound being used, but of the examplesof the organic solvent used in method (ii), those that can be usedinclude aromatic compounds, ethers, esters, hexane, kerosene,(meth)acrylic esters, and aromatic vinyl compounds.

When an acid salt is used as the copper salt, the acid component, whichis an anion, will be freed from the copper salt in the reaction betweenthe designated phosphoric ester compound and the copper salt. This acidcomponent is preferably removed as needed, because it can lead to adecrease in the thermal stability and moisture resistance of the resincomposition produced when component A and/or component B is dissolved ordispersed in a resin.

When a copper phosphate compound is manufactured by the above-mentionedmethod (i) or (ii), the acid component produced after the designatedphosphoric ester compound has reacted with the copper salt (the organicsolvent and the produced acid component in method (ii)) can be distilledoff.

When a copper phosphate compound is manufactured by the above-mentionedmethod (iii), a favorable method for removing the acid component is toadd an alkali to the organic solvent layer comprising the designatedphosphoric ester compound contained in an organic solvent, therebyneutralizing this layer, and then bring this organic solvent layer intocontact with the aqueous layer in which the copper salt is dissolved ordispersed, thereby reacting the designated phosphoric ester compound andthe copper salt, and then separate the organic solvent layer form theaqueous layer.

Examples of the alkali used here include sodium hydroxide, potassiumhydroxide, and ammonium, although this list is not comprehensive. Withthis method, a water-soluble salt is formed by the alkali and the acidcomponent freed from the copper salt, this salt moves into the aqueouslayer, and the designated phosphoric ester compound that is producedmoves into the organic solvent layer, so the acid component can beremoved by separating the aqueous layer from the organic solvent layer.

The number m of repeating units of the alkylene oxide groups in thephosphoric ester compounds expressed by Formulas (2), (3), (6), and (7)is an integer from 1 to 6, and preferably 1 to 3. If the value of m isover 6, there will be a severe decrease in hardness when a resincomposition is produced, for instance. On the other hand, if the valueof m is zero, that is, if no alkylene oxide group is bonded, then when aresin composition is produced it will be difficult to disperse thecopper ions in the resin.

The number k of repeating units of the alkylene oxide groups in Formula(8) is an integer from 0 to 5, and preferably 0 to 2. If the value of kis over 5, hardness will tend to decrease when a resin composition isproduced. The number r of repeating units of the alkylene oxide groupsin Formula (9) is an integer from 1 to 4. If the value of r is over 4,moisture absorption will be so high when a resin composition is producedthat a molded article will be prone to expansion and contraction. Inparticular, expansion and contraction caused by changes in humidity inthe surrounding environment can exacerbate the deterioration of asurface covering layer if such a layer is present, for example.

Also, if the value of r is over 4, the rigidity or hardness of a moldedarticle will decrease, and it will tend to be difficult to obtain thedesired mechanical strength that is necessary for a flat material.Furthermore, if the value of r is over 4, the resulting molded articlemay not have adequate heat resistance.

From the standpoint of the thermal stability of the phosphoric estercompound and the copper phosphate compound, it is particularly favorablefor the number m of repeating units of the alkylene oxide groups to be1.

Copper phosphate compounds and copper salts of phosphoric estercompounds having alkylene oxide groups in which this m is 1 tend to havea higher pyrolysis temperature than compounds having alkylene oxidegroups in which this m is 2 or greater, so the molding temperature canbe higher in the hot molding of compositions containing copper phosphatecompounds and copper salts of phosphoric ester compounds having alkyleneoxide groups in which m is 1. Thus, the molding is easier andworkability can be improved.

Also, copper phosphate compounds and copper salts of phosphoric estercompounds having alkylene oxide groups in which this m is 1 tend to havebetter moisture resistance than compounds having alkylene oxide groupsin which this m is 2 or greater. In specific terms, optical filters madefrom copper phosphate compounds and copper salts of phosphoric estercompounds having alkylene oxide groups in which this m is 1 undergosubstantially no deterioration over time in their visible lighttransmissivity in environments of high temperature and humidity, whereasthose having alkylene oxide groups in which this m is 2 or greater tendto deteriorate relatively readily over time.

As mentioned above, a monoester or diester is used as the designatedphosphoric ester compound, but with a triester, in which no hydroxylgroup is bonded in Formula (1), it is difficult to disperse the copperions in a resin when a resin composition is produced, for example,because there are no hydroxyl groups with which the copper ions canundergo coordination bonding and/or ion bonding.

R¹¹ to R¹⁷ in Formulas (2) to (6) are C_(1 to C) ₂₀ alkyl groups (with 1to 10 carbons being preferable, 1 to 4 being even better, and 1 or 2being particularly favorable), or C₆ to C₂₀ aryl groups or aralkylgroups (where the one or more hydrogen atoms bonded to the carbon atomsthat make up aromatic rings may be substituted with C₁ to C₆ alkylgroups or halogens).

R⁵¹ in Formula (7) and R⁵² in Formula (8) are C₁ to C₂₀ alkyl groupswith 1 to 10 carbons being preferable, 1 to 4 being even better, and 1or 2 being particularly favorable). When a phosphoric ester compound inwhich the carbon numbers of R¹¹ to R¹⁷ and R⁵¹ and R⁵² are over 20 ismade into a resin composition, there may be a drop in the miscibilitywith the resin, making it difficult to disperse the copper ions in theresin.

R²¹ in Formula (2), R²² in Formula (3), and R²³ to R²⁵ in Formula (6)are hydrogen atoms or C₁ to C₄ alkyl groups (where R²³, R²⁴, and R²⁵cannot all be hydrogen atoms). Specifically, examples of the alkyleneoxide groups in Formulas (2) and (3) include the buthylene oxide groupand propylene oxide group, and examples of the alkylene oxide groups inFormulas (6) include the butylene oxide group. Of these, compoundshaving propylene oxide groups are preferred.

If the carbon numbers of R²¹ to R²⁵ are over 4, it will be difficult todisperse component A and/or component B at a high proportion in asolvent or resin.

R³¹ in Formula (7) and R³² in Formula (8) are C_(1 to C) ₆ alkylenegroups (with 1 to 4 carbons being preferable, 3 or 4 being even better,and 3 being particularly favorable). Specifically, examples of alkyleneoxide groups (OR³¹ and OR³²) include a methyleneoxy group, ethyleneoxygroup, propyleneoxy group, butyleneoxy group, pentyleneoxy group, andhexyleneoxy group, with a propyleneoxy group and butyleneoxy group beingparticularly favorable.

If the carbon numbers of R³¹ and R³² are over 6, it will be difficult todisperse component A and/or component B at a high proportion in asolvent or resin. R⁴¹ in Formula (8) is a C₁ to C₁₀ alkylene group (with3 to 6 carbons being preferable, 3 or 4 being even better, and 3 beingparticularly favorable). R⁶¹ in Formula (9) is a hydrogen atom or methylgroup.

With the optical filter of the present invention, which comprises a nearinfrared light absorption layer containing component A and/or componentB, the phosphoric acid groups of the designated phosphoric estercompound are bonded to the copper ions by coordination bonding and/orion bonding, these copper ions are dissolved or dispersed in the nearinfrared light absorption layer in a state of being surrounded by thephosphoric ester, and near infrared light is selectively absorbedthrough electronic transition between the d orbits of these copper ions.

Here, the proportion in which the copper ions are contained in the nearinfrared light absorption layer composed of component A and/or componentB should be adjusted to 2 to 60 wt %, and preferably 2 to 20 wt %, andeven more preferably 2 to 15 wt %, with respect to the entire nearinfrared light absorption layer. If this copper ion content is less than2 wt %, then when the thickness of the optical filter or near infraredlight absorption layer is reduced to about 1 mm, it will tend to bedifficult to obtain satisfactory near infrared light absorption.

On the other hand, if the copper ion content is over 60 wt %, it willtend to be difficult to disperse the copper ions in the near infraredlight absorption layer. As mentioned above, the near infrared lightabsorption layer will exhibit the same tendency when formed from a resincomposition containing component A and/or component B.

The above-mentioned metal ions are preferably used in a proportion of nomore than 50 wt % out of all the metal ions including the copper ions.30 wt % or less is even better, and 20 wt % or less is especiallyfavorable. If this proportion is over 50 wt %, the bonding coordinationbetween the copper ions and the phosphoric ester compound will beaffected by the other metal ions, and the near infrared light absorptionwill tend not to be raised sufficiently.

The ratio in which the designated phosphoric ester compound and thecopper ions are contained in the near infrared light absorption layer isadjusted so that the phosphorus atom content in the near infrared lightabsorption layer will be 0.4 to 1.3 mol per mole of copper ions, thatis, so that the P/Cu molar ratio will be 0.4 to 1.3, and preferably 0.8to 1.3.

If the P/Cu molar ratio is less than 0.4, there will be an excess ofcopper ions coordinated with respect to the designated phosphoric estercompound, and the copper ions will tend not to disperse uniformly in thenear infrared light absorption layer. The same tendency is seen when thenear infrared light absorption layer is formed from the above-mentionedresin composition.

On the other hand, if the P/Cu molar ratio is over 1.3, devitrificationwill tend to occur more readily when the thickness of the optical filteris reduced and the copper ion content is raised as mentioned above so asto be at least 2 wt % versus the with respect to the entire nearinfrared light absorption layer, and this tendency will be particularlypronounced in environments of high humidity and temperature.

Therefore, with the optical filter of the present invention, the P/Cumolar ratio in the near infrared light absorption layer is set tobetween 0.4 and 1.3, so the copper ions are uniformly dispersed in thenear infrared light absorption layer, good near infrared lightabsorption is obtained, and even if the thickness is reduced and thecopper ion content raised, it will still be possible to obtain anoptical filter with extremely good moisture resistance.

In particular, the dispersibility of the copper ions in the resin can bereliably and sufficiently raised if this molar ratio is at least 0.8.Thus, if the P/Cu molar ratio in the near infrared light absorptionlayer is set to between 0.8 and 1.3, the copper ions will be uniformlydispersed in the near infrared light absorption layer, even better nearinfrared light absorption will be obtained, and an optical filter witheven more superior moisture resistance can be obtained.

Furthermore, if the designated phosphoric ester compound is such thatR⁶¹ in Formula (9) is a methyl group, p in Formula (9) is 2 or 3, and rin Formula (9) is 1 (that is, if it is the phosphoric ester compoundexpressed by Formula (10), or the phosphoric ester compound expressed byFormula (11)), then the near infrared light absorption will be markedlyhigher than with a phosphoric ester compound having methacryloyloxyalkylgroups expressed by Formula (9) and including alkylene oxide groups inwhich p is at least 4.

It is therefore possible to raise the selective absorption of nearinfrared light of the optical filter, and to raise its selectivetransmission of visible light. If r (the repeat number of these alkyleneoxide groups) is 1, there will be substantially no deterioration in thevisible light transmissivity of the optical filter over time. Thus, theimprovement in the moisture resistance of the optical filter will beeven better. In contrast, with an optical filter in which r is 2 orgreater, and especially one in which the number of alkylene oxide groupsis an integer over 4, there will be a tendency for moisture resistance,rigidity, heat resistance, and so forth to deteriorate more readily overtime.

Of the phosphoric ester compounds expressed by Formula (1), if a mixtureof a phosphoric ester compound having an aromatic ring and a phosphoricester compound not having an aromatic ring is used, the resultingoptical filter will have improved transmissivity on the visible lightside in the wavelength band at the boundary between visible light andnear infrared light (a wavelength of roughly 750 nm), and improvedabsorption on the near infrared light side in this wavelength band.

In particular, if the phosphoric ester compound having an aromatic ringis a compound expressed by Formula (25)-a and/or Formula (25)-b, andpreferably Formula (25)-b, the selective absorption of near infraredlight and the selective transmission of visible light will be superior,and the solubility of component A and/or component B in a solvent willbe higher in obtaining a liquid composition (discussed below).

The ratio in which the phosphoric ester compound having an aromatic ringand/or a copper compound thereof, and the phosphoric ester compound nothaving an aromatic ring and/or a copper compound thereof are containedhere is a weight ratio of from 10:90 to 90:10, and preferably 40:60 to90:10, with a range of 60:40 to 85:15 being particularly favorable.

The near infrared light absorption layer that makes up the opticalfilter of the present invention may be formed from just component Aand/or component B, or it may be formed from a resin composition inwhich these components are contained in a resin, as discussed above. Thenear infrared light absorption layer may also be formed by dissolving ordispersing the above-mentioned components in a solvent, coating asubstrate with the resulting liquid composition, and evaporating off thesolvent. Naturally, the entire optical filter may also be formed fromthe near infrared light absorption layer.

Liquid compositions, resin compositions, and adhesive resin compositions(a kind of resin composition) that are favorable for forming the nearinfrared light absorption layer will now be described.

Liquid Compositions

As discussed above, a liquid composition comprises component A and/orcomponent B dissolved or dispersed in a solvent, and as long as thethin-film near infrared light absorption layer produced by evaporatingoff the solvent will be optically transparent, the liquid compositionitself may be transparent, semi-transparent, or opaque.

The solvent here can be water or an organic solvent. Examples of organicsolvents include methyl alcohol, ethyl alcohol, isopropyl alcohol, butylalcohol, and other alcohols; methyl cellosolve, ethyl cellosolve, andother glycol ethers; diethyl ether, diisopropyl ether, and other ethers;acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, andother ketones; ethyl acetate, isopropyl acetate, butyl acetate, butylcellosolve acetate, and other esters; benzene, toluene, xylene, andother aromatic compounds; and hexane, kerosene, and petroleum ether.

Other solvents that can be used are polymerizable organic solvents suchas the monomer that makes up the resin (as described under the heading“Resin composition” below) such as a (meth)acrylate or other(meth)acrylic ester, styrene, α-methylstyrene, or another such aromaticvinyl compound.

The proportion in which component A and/or component B is contained inthis liquid composition will vary with the type of solvent used and withthe application or intended use of the optical filter, but from thestandpoint of viscosity after preparation, the amount is usuallyadjusted to a range of 0.1 to 1900 mass parts, and preferably 1 to 900mass parts, and even more preferably 5 to 400 mass parts, per 100 massparts solvent.

The optical filter of the present invention can be obtained with thegreatest of ease by using this liquid composition to coat a thin glassor resin material (such as a thin resin sheet or film) or the like thatis translucent to visible light. It is simplicity itself to provide athin-film optical filter on a surface having any of various sizes orshapes merely by coating the desired location or side of an article withthis liquid composition, and this is extremely useful when the opticalfilter is provided over a large surface area. Furthermore, if thesolvent is a resin or monomer, it will be exceedingly easy to obtain anear infrared light absorption material in the form of a thin film of aresin or the like.

Resin Composition

The above-mentioned component A and component B both have excellentmiscibility with resins, and since the copper ions are dispersed well inthe resin, as mentioned above, a resin composition having excellent nearinfrared light absorption can be obtained. This resin composition may bea monomer composition, or a polymer composition may be obtained bypolymerizing a monomer composition.

There are no particular restrictions on the monomer that makes up thisresin composition as long as it is a resin with excellent dispersibilityin component A and/or component B, but the following acrylic resins, ormonomers other than acrylic resins, can be used to advantage.

A polymer obtained from a (meth) acrylic ester monomer can be usedfavorably as an acrylic resin. Specific examples of (meth)acrylic estermonomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl(meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate,tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl(meth)acrylate, and other alkyl (meth) acrylates; glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,hydroxybutyl (meth)acrylate, isobornyl (meth)acrylate,methoxypolyethylene (meth)acrylate, phenoxy (meth)acrylate, and othermodified (meth)acrylates; and ethylene glycol di(meth)acrylate,diethylene glycol di(meth)acrylate, polyethylene glycoldi(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,3-butyleneglycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, neopentyl glycol di(meth)acrylate,2-hydroxy-1,3-di(meth)acrylate,2,2-bis[4-(meth)acryloxyethoxyphenyl]propane,2-hydroxy-1-(meth)acryloxy-3-(meth)acryloxypropane, trimethylolpropanetri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, and other polyfunctional (meth)acrylates.

Putting “meth” in parentheses as above is a notational method used forthe sake of convenience and simplicity when there is a need to indicateboth acrylic acid or derivatives thereof and methacrylic acid orderivatives thereof, and this method is employed in the presentinvention as well.

Another acrylic resin that can be used in a copolymer of theabove-mentioned (meth)acrylic ester monomer with another monomer that iscopolymerizable with this (meth)acrylic ester monomer.

Specific examples of such copolymerizable monomers include (meth)acrylicacid, 2-(meth)acryloyloxyethyl-succinic acid,2-(meth)acryloyloxyethylphthalic acid, and other unsaturated carboxylicacids; N,N-dimethylacrylamide, and other acrylamides; and styrene,α-methylstyrene, chlorostyrene, dibromostyrene, methoxystyrene,vinylbenzoic acid, hydroxymethylstyrene, and other aromatic vinylcompounds. Examples of other resins besides acrylic resins includepolyethylene terephthalate (PET), polyethylene, polypropylene, polyvinylchloride, polycarbonate, and styrene, α-methylstyrene, chlorostyrene,dibromostyrene, methoxystyrene, vinylbenzoic acid, hydroxymethylstyrene,and other aromatic vinyl compounds, and other such polymers. The abovemonomers can be used singly or in combinations of two or more types.

When just a monofunctional monomer is used, a thermoplastic resin willbe obtained, but when all or part of the monomer is polyfunctional, athermosetting resin will be obtained, so these resin compositions can besuitably selected so as to obtain an optical filter suited to theintended use, application, molding method, and so forth. Of these, if athermoplastic resin is used, remolding will be easier afterpolymerization curing, which makes it easier to work the optical filter.

The resin composition is prepared by adding component A and/or componentB to the above-mentioned resin. The proportion in which component Aand/or component B is contained will vary with the application orintended use of the optical filter, but from the standpoint offormability (or moldability), the amount is usually adjusted to a rangeof 0.1 to 400 mass parts, and preferably 0.3 to 200 mass parts, and evenmore preferably 1 to 100 mass parts, per 100 mass parts resin.

The proportion of copper ions in the resin composition should beadjusted to a range of 2 to 60 wt %, and preferably 2 to 20 wt %, andeven more preferably 2 to 15 wt %, with respect to the overall resincomposition. There are no particular restrictions on the specific methodused to prepare the resin composition, but the following two methods arefavorable.

First Method

This first method involves preparing a monomer composition by addingcomponent A and/or component B to a monomer, and then subjecting thismonomer composition to radical polymerization. In this method, there areno particular restrictions on the specific method for conducting theradical polymerization of the monomer composition, and any ordinaryradical polymerization method that makes use of a radical polymerizationinitiator can be used, such as bulk (cast) polymerization, suspensionpolymerization, emulsion polymerization, solution polymerization, andother such known methods.

Second Method

This second method involves adding component A and/or component B to aresin and mixing. This method is employed when the resin isthermoplastic. More specifically, this can be (1) a method in whichcomponent A and/or component B is added to and kneaded with a moltenresin or (2) a method in which a resin is dissolved or dispersed in, orswollen with, a suitable organic solvent, component A and/or component Bis added to and mixed with this solution, and the organic solvent isthen removed from the solution.

In method (1) above, the kneading of the resin with component A and/orcomponent B can be accomplished by any process that is commonly used inthe melt kneading of thermoplastic resins, examples of which includemelt kneading with a mixing roll, and pre-mixing in a Herschel mixer orthe like and then melt kneading in an extruder.

There are no particular restrictions on the organic solvent used in theabove method (2) as long as it allows the above-mentioned resin to bedissolved, dispersed, or swollen, but specific examples include methylalcohol, ethyl alcohol, isopropyl alcohol, and other alcohols; acetone,methyl ethyl ketone, and other ketones; benzene, toluene, xylene, andother aromatic compounds; methylene chloride and other chlorinatedhydrocarbons; and dimethylacrylamide, dimethylformamide, and other amidecompounds.

In the preparation of the above-mentioned resin composition, whencomponent A is used and a copper salt of an organic or inorganic acid isused as the copper salt, the result of the reaction between thedesignated phosphoric ester compound and the copper salt will be thefreeing of the acid component (an anion) from the copper salt. This acidcomponent is preferably removed as needed. This can be accomplished by(a) a method in which the acid component is extracted by immersing theresin composition in a suitable organic solvent, or (b) a method inwhich the acid component is precipitated out by cooling the monomercomposition prior to its polymerization.

It is preferable for water to be present during the preparation of theresin composition. Specifically, it is preferable for the optical filterto be manufactured by a method comprising a step or mixing or bringinginto contact the designated phosphoric ester compound expressed byFormula (1), a copper salt, and water. Put another way, it is preferablefor water to be present when the designated phosphoric ester compoundand the copper salt are mixed or brought into contact.

This affords a sufficient increase in the stability of the monomercomposition. Furthermore, it is possible to increase the transparency ofthe polymer (the near infrared light absorption layer of the opticalfilter) obtained by polymerizing the monomer composition. An example ofhow the water is made to be present here is to add water in thepreparation of the monomer composition. More specifically, for example,the designated phosphoric ester compound and the copper salt are addedto the monomer that makes up the resin, after which liquid water orgaseous water (steam) is added or introduced. An advantage to this isthat it will be easier to dissolve or disperse component A and/orcomponent B in the resin monomer.

This method in which water is added is particularly favorable whencopper acetate, copper acetate monohydrate, copper benzoate, or anothersuch copper salt anhydride or hydrate of an organic acid is used as thecopper salt. When copper hydroxide, basic copper carbonate, or the likeis used as the copper salt, there is no need to remove the acidcomponent as discussed above, but it is preferable to perform refluxdehydration at normal or reduced pressure during the preparation of themonomer composition. This affords the same benefits as when water ismade to be present when a copper salt anhydride or hydrate is used asthe copper salt, as discussed above.

The reason for this seems to be that adding water to the monomercomposition when there is not enough, or removing water when there is anexcess amount, increases the stability of the monomer composition, andimproves the transparency of the polymer obtained when this monomercomposition is polymerized. More exactly, it is surmised that there is apreferable range for the amount of water contained in the monomercomposition or polymer thereof, which is neither excessive norinadequate. Other action mechanisms may instead apply, however.

It is preferable for the monomer composition obtained in this way tocontain 0.1 to 5 wt % water (moisture). If this moisture content isunder 0.1 wt %, the stability of the monomer composition may not besufficient, and the transparency of the polymer thereof may not beadequately increased. On the other hand, if the moisture content is over5 wt %, the polymer may undergo whitening, in which case there is amarked decrease in the transparency of the polymer.

There are no particular restrictions on the organic solvent used in theabove method (a) as long as it can dissolve the freed acid component andhas appropriate affinity with the resin being used (affinity to theextent that it will penetrate into the resin, but will not dissolve it).

Specific examples of such solvents include methyl alcohol, ethylalcohol, n-propyl alcohol, isopropyl alcohol, and other lower aliphaticalcohols; acetone, methyl ethyl ketone, and other ketones; diethylether, petroleum ether, and other ethers; n-heptane, n-hexane, n-butane,chloroform, methylene chloride, carbon tetrachloride, and otheraliphatic hydrocarbons and halides thereof; and benzene, toluene,xylene, and other aromatic compounds.

Meanwhile, in the above method (b), it is preferable for the copper saltthat makes up component A to be one with which the freed acid componentwill not readily dissolve in the monomer, or a copper salt other than anorganic acid or inorganic acid salt. Specific examples include copperhydroxide and copper salts of carboxylic acids having an aromatic-ring,such as benzoic acid.

Adhesive Resin Composition

Among compositions containing a resin other than an acrylic resin, thosethat contain a polyvinyl butyral resin, an ethylene-vinyl acetatecopolymer, or a partial saponification product of this copolymer willhave superior adhesion to base materials composed of glass or plastic,and will themselves be flexible, and will have little temperaturedependence.

Therefore, such a resin composition containing component A and/orcomponent B is an adhesive resin composition, and will provide goodadhesion to the substrate even if an adhesive agent is not used. Thus,an optical filter with excellent workability can be obtained moreeasily, and the resulting optical filter will have greater resistance totemperature changes.

Various plasticizers that are miscible with the resin can be added asother components to the above-mentioned resin composition so as toenhance the dispersibility of the copper ions in the resin component.Specific examples of such plasticizers include tricresyl phosphate,triphenyl phosphate, and other phosphoric ester-based plasticizers;dioctyl phthalate, dibutyl phthalate, and other phthalic acid-basedplasticizers; dibutyl sebacate, butyl ricinoleate, methylacetylricinoleate, butyl succinate, and other fatty acid-based plasticizers;and butylphthalylbutyl glycolate, triethylene glycol dibutyrate,triethylene glycol di-2-ethyl butyrate, polyethylene glycol, and otherglycol-based plasticizers.

Benzotriazole-, benzophenone-, or salicylic acid-based ultravioletabsorbents, other antioxidants, stabilizers, and so forth can also beadded.

Examples of favorable application of an optical filter equipped with theabove-mentioned near infrared light 4 absorption layer (as mentionedabove, the entire optical filter may also be a near infrared lightabsorption layer) will now be given.

Display Panel

It is extremely favorable for the optical filter of the presentinvention to be applied to a so-called display panel, which is anelectronic display panel such as a plasma display panel (PDP). Some ofthe emitters provided to these electronic displays emit near infraredlight with a wavelength of 800 to 1100 nm, and a problem is that nearinfrared light emitted from the panel of an electronic display can causemalfunction in television and other near infrared light remote controlsystems (infrared remotes) used near the electronic display.

In particular, with a PDP, the rare gas (xenon or neon) in the spacebetween the emitter electrodes is subjected to discharge excitation, anda higher intensity near infrared light is emitted than with other kindsof electronic display. In view of this, there is a need for a displaypanel with better absorption of near infrared light and transmission ofvisible light.

If the optical filter of the present invention is applied to thesubstrate (made of glass or resin) of a display panel, for example, itis possible to obtain a display panel with excellent selectiveabsorption of near infrared light and selective transmission of visiblelight. Furthermore, because of the increased moisture resistance of theoptical filter, devitrification of the display panel can be preventedover an extended period, which extends the service life of the displaypanel.

Also, if the substrate is coated with component A and/or component Bitself, or with the above-mentioned liquid composition, and this coatingis dried, an optical filter composed of a thin-film near infrared lightabsorption layer will be formed on the surface of the display panel. Anexample of such a display panel will now be described.

FIG. 1A is a schematic cross section illustrating an example of adisplay panel in which the optical filter of the present invention isused, and FIG. 1B is an exploded perspective view illustrating thelayered structure of the display panel shown in FIG. 1A.

A display panel 1 has the optical filter 16 of the present inventionapplied to one side of a transparent member 11 that serves as anoptically transparent panel attached to the front of a PDP, and a shieldmesh 13 (a mesh in which electroconductive wires are woven verticallyand horizontally) is applied and covered with a transparent film 14 madeof a resin (such as polyethylene terephthalate (PET)). A reflectionreducing film 12 is formed over the entire other side of the transparentmember 11. An anti-reflective film 15 is formed on the side of thetransparent film 14 not in contact with the shield mesh 13.

The following three types are favorable for the optical filter 16 formedon the transparent member 11.

First Type:

Component A and/or component B is applied by coating or lamination overthe transparent member 11, or the above-mentioned liquid composition oradhesive resin composition is applied by coating or lamination, and thisis dried to produce a thin film.

Second Type:

A thin sheet or film composed of the above-mentioned resin composition.

Third Type:

Component A and/or component B is applied by coating or lamination to athin transparent material (sheet, film, etc.), or the above-mentionedliquid composition or adhesive resin composition is applied by coatingor lamination, or a film composed of the above-mentioned resincomposition is laminated.

The resin used in the above-mentioned resin composition is preferably anacrylic resin, polycarbonate resin, styrene resin, polyester resin, orcellulose resin, and from the standpoints of visible light transmission,weatherproofness, workability, and so on, an acrylic resin isparticularly favorable. When a resin composition composed of an acrylicresin is used, the image displayed on the display panel will be brightenough for easy viewing, and the display panel 1 can be obtained withexcellent durability and few limitations on the shape into which it isworked.

With a display panel 1 equipped with a transparent member 11 containingan optical filter 16 of each of the above types, the type of component Aand/or component B in the optical filter of the present invention, theconcentration, and the layer thickness (the thickness of the layeritself in the case of coating or lamination, or the thickness of theresin layer when these components are dispersed in the resin) areadjusted so that the transmissivity of near infrared light of thedisplay panel 1 in a wavelength band of 800 to 1100 nm will be 20% orless, and preferably 15% or less, and even more preferably 10% or less.

Such adjustment will sufficiently attenuate near infrared light with awavelength of around 950 nm, which is used primarily in infraredcommunications and so on, so infrared remotes and the like will be lesslikely to malfunction when used around the display.

If the shield mesh 13 is woven from plastic fibers covered with atransition metal such as copper or nickel, for instance, electromagneticwaves with a frequency ranging from a few megahertz to about 1 GHz canbe effectively and reliably blocked. The reflection reducing film 12 andthe anti-reflective film 15 can be formed, for example, by alternatelylaminating a thin film composed of a material with a low refractiveindex, such as silicon dioxide or aluminum oxide, and a thin film of amaterial with a high refractive index, such as titanium dioxide oryttrium oxide.

FIG. 2 is a perspective view illustrating an example of how the displaypanel in FIG. 1 is used. As shown in FIG. 2, the display panel 1 isoriented so that the side on which the anti-reflective film 15 is formedis at the front and covers the screen 21 of the PDP 2. Near infraredlight emitted from the screen 21 of the PDP 2 is absorbed by the opticalfilter 16, and its intensity is reduced to 20% or less, and preferably15% or less, and even more preferably 10% or less.

Meanwhile, almost none of the visible light emitted from the screen 21of the PDP 2 at the same time as the near infrared light is absorbed bythe optical filter 16 provided to the display panel 1. Therefore, evenif devices that operate with near infrared light are placed around thePDP 2 shown in FIG. 2, the near infrared light emitted from the screen21 of the PDP 2 is effectively prevented from causing these devices tomalfunction, and the image shown on the screen 21 can be viewed withoutany problem.

Electromagnetic waves are emitted from the screen 21 of the PDP 2, butsince these electromagnetic waves are effectively blocked by the shieldmesh 13 shown in FIGS. 1A and 1B, the viewer is not exposed to theseelectromagnetic waves while viewing the PDP 2.

Furthermore, since this shield mesh 13 is just as electroconductive as ametal, almost no electrostatic charge builds up on the display panel 1,which prevents dust and so forth from clinging to the display panel 1due to static electricity. Also, the display panel 1 can be made morelightweight if the shield mesh 13 is made mainly from plastic fibers.Moreover, the shield mesh 13 is very flexible, which is an advantage inthat it can be easily applied even if the display panel 1 has a bumpysurface.

When external light (mainly natural light or light from lamps) that isincident on the screen 21 from the display panel 1 side hits theanti-reflective film 15 of the display panel 1, its reflection isprevented by the action of the multiple layers of different refractiveindexes that form the anti-reflective film 15.

As a result, even if the PDP is in a brightly lit area, there will be noreflection of external light that would make the image on the screen 21difficult to view. A tiny portion of the external light here does passthrough the anti-reflective film 15, but the reflection of thistransmitted light is reduced by the reflection reducing film 12. Thus,reflection of external light that would make it difficult to view theimage shown on the screen 21 can be prevented even better.

Near infrared light and infrared light are heat rays, and it is alsofavorable for the optical filter of the present invention to belaminated or formed on members where heat rays need to be absorbed. Aheat ray-absorbent coating, a heat ray-absorbent composite, and a heatray-absorbent material that makes use of a heat ray-absorbent adhesivewill now be described as specific application examples.

Heat Ray-Absorbent Coating

The product of dissolving or dispersing component A and/or component Bin a suitable solvent (that is, the above-mentioned liquid composition)is applied to the surface that needs coating, and the solvent isevaporated off to form a thin film over all or part of the surface. Thisthin film is the optical filter (near infrared light absorption layer)of the present invention, and serves as a heat ray-absorbent coatingwith excellent near infrared light absorption and moisture resistance.If the thin-film optical filter thus formed is optically transparent,then the liquid composition itself may be transparent, semitransparent,or opaque.

An additive such as a dissolution auxiliary may be added to the liquidcomposition in order to raise the solubility or dispersibility ofcomponent A and/or component B in the solvent, or to increase theflatness and so forth of the side with the heat ray-absorbent coating,that is, the side on which the optical filter is formed. Examples offavorable additives include various surfactants used as anti-foamingagents and leveling agents.

The proportion in which component A and/or component B is contained inthe liquid composition used for a heat ray-absorbent coating will varywith the type of liquid solvent being used, and the application orintended use of the heat ray-absorbent coating agent, but from thestandpoint of viscosity after preparation, it is usually favorable toadjust the amount to a range of 0.1 to 1900 mass parts, and preferably 1to 900 mass parts, and even more preferably 5 to 400 mass parts, per 100mass parts liquid solvent.

Heat Ray-Absorbent Composite

It is useful for the heat ray-absorbent composite to be produced bylaminating or forming the optical filter of the present invention on oneside of a translucent substrate. Another translucent substrate may alsobe laminated over this optical filter.

There are no particular restrictions on the material of the substrate aslong as it transmits visible light, and the material should be selectedas dictated by the application of the heat ray-absorbent composite, butfrom the standpoints of hardness, heat resistance, chemical resistance,durability, and so forth, it is preferable to use a glass material suchas inorganic or organic glass, or a plastic material such aspolycarbonate, acrylonitrile-styrene copolymer, polymethyl methacrylate,vinyl chloride resin, polystyrene, or polyester.

The substrate may consist of the same type of materials, or may consistof mutually different materials. Furthermore, it is preferable toperform a hardening treatment on the side on which the optical filter isnot laminated or formed because this will prevent scratches and enhancedurability on that side. A layer composed of another light transmittingmaterial may be further provided to the substrate. This results in aheat ray-absorbent composite with superior near infrared lightabsorption and moisture resistance.

A reflection reducing layer or anti-reflective layer may also beprovided to at least one face of the optical filter and the substrate ofthe heat ray absorbent composite. This reflection reducing layer oranti-reflective layer can be formed by using a known material composedof an inorganic oxide, inorganic halide, or the like and any of variousknown methods such as vacuum vapor deposition, ion plating, andsputtering. If needed, a visible light absorbent that absorbs visiblelight of a specific wavelength, such as a metal ion-containing componentcontaining cobalt ions that selectively absorb at a wavelength of 500 to600 nm, or another additive may also be mixed with the resincomposition.

Heat Ray-Absorbent Material that Makes Use of a Heat Ray-AbsorbentAdhesive

It is useful for the heat ray-absorbent adhesive to contain aself-adhesive resin and component A and/or component B. A self-adhesiveacrylic resin can be used favorably as this self-adhesive resin. This isobtained by polymerizing a monomer composition containing a monomer ofthe acrylic resin that makes up the adhesive component.

An acrylic acid alkyl ester in which the carbon number of the alkylgroups is 4 to 12 and the glass transition point of the homopolymer isfrom −70 to −30° C. can be used favorably as this acrylic resin monomer,specific examples of which include n-butyl acrylate, 2-ethylhexylacrylate, octyl acrylate, and decyl acrylate.

The monomer composition used to obtain a self-adhesive acrylic resinpreferably contains a monomer that constitutes an agglomerationcomponent and a monomer that constitutes a modification component inaddition to the acrylic resin monomer used as the above-mentionedself-adhesive component.

The monomer having the agglomeration component is one that can becopolymerized with the acrylic resin monomer used as the self-adhesivecomponent, and has the action of raising the glass transition point ofthe copolymer thus obtained. Specific examples include acrylic acidalkyl esters having a C₁ to C₃ lower alkyl group, methacrylic acid alkylesters, vinyl acetate, vinylidene chloride, acrylonitrile, and styrene.

The monomer used as the modification component is one that can becopolymerized with the acrylic resin monomer used as the self-adhesivecomponent, and has functional groups. Specific examples include acrylicacid, methacrylic acid, maleic acid, maleic acid monoesters, and othercarboxyl-containing compounds; 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, and other hydroxyl-containing compounds; acrylamide,methacrylamide, N-tert-butylacrylamide, N-octylacrylamide, and otheracid amide compounds; and glycidyl acrylate, glycidyl methacrylate, andother glycidyl-containing monomers.

The proportions in which the various monomers are used in theabove-mentioned monomer composition will vary with the type of monomerbeing used, the intended use of the obtained acrylic resin composition,and so on, but usually the acrylic resin monomer used as theself-adhesive component accounts for 30 to 95 mass %, the monomer usedas the agglomeration component for 5 to 50 mass %, and the monomer usedas the modification component for 0.1 to 10 mass %. Solutionpolymerization or emulsion polymerization can be used as the method forpolymerizing this monomer composition.

Examples of catalysts that can be used in this polymerization includebenzoyl peroxide, ammonium persulfate, azobisisobutyronitrile, potassiumpersulfate, and other peroxides. When the polymerization of the monomerresin composition is accomplished by solution polymerization, any ofvarious organic solvents can be used as the polymerization solvent,examples of which include ethyl acetate and other esters, aromatichydrocarbons, and ketones. When the monomer composition is polymerizedby emulsion polymerization, any of various known compounds ordinarilyused in emulsion polymerization can be used as an emulsifier.

Polymerizing the monomer composition yields a self-adhesive acrylicresin in the form of a polymer solution or latex. Component A and/orcomponent B is mixed into the polymer solution or latex thus obtained,and this mixture is applied by coating or lamination so as to be thinlystretched over the substrate, for example, thereby forming aself-adhesive optical filter.

If needed, a visible light absorbent that absorbs visible light of acertain wavelength, such as a metal ion-containing component containingcobalt ions that selectively absorb at a wavelength of 500 to 600 nm, orother additives may be mixed into the above mixture.

The proportion in which component A and/or component B is contained inthe heat ray-absorbent adhesive should be as large as possible to theextent that the translucence and adhesion of the self-adhesive acrylicresin are not compromised, and it is favorable to adjust the amount to arange of 0.1 to 400 mass parts, and preferably 0.3 to 200 mass parts,and even more preferably 1 to 100 mass parts, per 100 mass partsself-adhesive acrylic resin.

A heat ray-absorbent material on which a self-adhesive optical filterhas been formed can be easily obtained by coating a transparentsubstrate with this heat ray-absorbent adhesive. The above-mentionedheat ray-absorbent composite can be easily obtained by laminating asubstrate over this optical filter, without using an adhesive for thislamination.

The heat ray-absorbent coating, heat ray-absorbent composite, and heatray-absorbent material that makes use of a heat ray-absorbent adhesivedescribed above can be favorably applied to translucent members withwhich heat rays need to be blocked, for instance. Specific examplesinclude windows for homes and other buildings, windows for automobiles,trains, and other such vehicles, windows for aircraft, ships, and othersuch vehicles, and other members that provide light and a view.

Compared to when a light blocking member that absorbs visible light isused in order to block out heat rays, these window materials havesuperior visible light transmission while offering equivalent or betterheat ray absorption, so they afford excellent visibility of what isoutside the window, and tend to provide a more spacious feel. Also,since the optical filter of the present invention has excellent moistureresistance, when a window or the like having this optical filter is usedoutdoors or another place where it will be exposed to high temperatureand humidity, an advantage is that devitrification will be less apt tooccur, and good heat ray absorption can be maintained for an extendedperiod.

Another example of an application is an agricultural covering materialused to construct a greenhouse for enclosing a plant cultivation area.The purpose of a greenhouse is to maintain the internal temperature, butthere is the danger that in the summertime heat rays from the outsidemay raise the internal temperature higher than necessary. If anagricultural covering material that has been given the above-mentionedheat ray-absorbent coating, or an agricultural covering material formedfrom the above-mentioned heat ray-absorbent composite or heatray-absorbent material is used, excessive elevation of the temperatureinside a greenhouse or the like is effectively suppressed, which extendsthe usable life of the greenhouse and makes it more cost effective.Also, since visible light transmission is excellent, there will also bean improvement in visibility of the interior from outside thegreenhouse. Furthermore, because the optical filter of the presentinvention has excellent moisture resistance, when an agriculturalcovering material equipped with this optical filter is used outdoors,etc., there will be less devitrification, which is an advantage in thatgood heat ray absorption can be preserved for an extended period.

EXAMPLES

Specific examples pertaining to the present invention will now bedescribed, but the present invention is not limited to these examples.

Example 1

(1) A monomer solution was obtained by mixing 16 g of the phosphoricester compound expressed by Formula (28)-s (hereinafter referred to as“phosphoric ester A”), 14.4 g of the phosphoric ester compound expressedby Formula (28)-t (hereinafter referred to as “phosphoric ester B”), 20g of diethylene glycol dimethacrylate, 48.6 g of methyl methacrylate,and 0.9 g of α-methylstyrene.

(2) 32 g of copper benzoate (cupric benzoate; the same applieshereinafter) was added to and dissolved in this monomer solution, afterwhich this solution was left for 24 hours in a −20° C. refrigerator tocrystallize and precipitate the benzoic acid (melting point: 122° C.)

(3) The precipitated benzoic acid was filtered off the monomer solutionat an environment temperature of −20° C.

(4) 2.0 g of tert-butyl peroctanoate was added as a polymerizationinitiator to this monomer solution. This monomer solution was pouredinto a polymerization cell comprising two glass sheets and a PVC gasket,and heated at successively varying temperatures for 16 hours at 45° C.,8 hours at 60° C., and 3 hours at 100° C., which yielded a light blue,transparent optical filter in the form of a sheet 0.5 mm thick (Thisentire optical filter was a near infrared light absorption layer).

(5) The phosphorus atom content in this optical filter was 1.13 mol permole of copper ions (that is, a P/Cu molar ratio of 1.13). The copperion content in the optical filter was 6.1 wt %.

Example 2

Other than using 17.3 g of phosphoric ester A, 15 g of phosphoric esterB, and 46.7 g of methyl methacrylate, a light blue, transparent opticalfilter in the form of a sheet 0.5 mm thick was obtained in the samemanner as in Example 1 above. The P/Cu molar ratio of this opticalfilter was 1.20. The copper ion content in the optical filter was 6.1 wt%.

Example 3

Other than adding 0.7 g of water to the monomer solution, a light blue,transparent optical filter in the form of a sheet 0.5 mm thick wasobtained in the same manner as in Example 2 above. The P/Cu molar ratioof this optical filter was 1.20. The copper ion content in the opticalfilter was 6.1 wt %.

Comparative Example 1

Other than using 12 g of phosphoric ester A, 11.7 g of phosphoric esterB, 55.3 g of methyl methacrylate, and 20 g of copper benzoate, a lightblue, transparent optical filter in the form of a sheet 0.5 mm thick wasobtained in the same manner as in Example 1 above. The P/Cu molar ratioof this optical filter was 1.42. The copper ion content in the opticalfilter was 3.9 wt %.

Comparative Example 2

Other than using 21.5 g of phosphoric ester A, 23.5 g of phosphoricester B, and 34 g of methyl methacrylate, a light blue, transparentoptical filter in the form of a sheet 0.5 mm thick was obtained in thesame manner as in Example 1 above. The P/Cu molar ratio of this opticalfilter was 1.71. The copper ion content in the optical filter was 6.1 wt%.

Comparative Example 3

Other than using 14.5 g of phosphoric ester A, 14 g of phosphoric esterB, and 50.5 g of methyl methacrylate, a light blue, transparent opticalfilter in the form of a sheet 0.5 mm thick was obtained in the samemanner as in Example 3 above. The P/Cu molar ratio of this opticalfilter was 1.71. The copper ion content in the optical filter was 3.9 wt%.

Spectral Transmittance Measurement

Using a spectrophotometer “U-4000” (made by Hitachi) the spectraltransmittance at a wavelength of 250 to 1200 nm was measured for theoptical filters produced in Examples 1 to 3 and Comparative Examples 1to 3. FIGS. 3 to 7 show the spectral transmittance spectra for theoptical filters of Examples 1 and 2 and Comparative Examples 1 to 3.These results confirmed that the optical filters of the presentinvention had sufficient visible light transmission and near infraredlight absorption. The optical filter in Example 3 had transparency equalto or greater than that of the optical filter in Example 2.

Moisture Resistance Test

The optical filters produced in Examples 1 to 3 and Comparative Examples1 to 3 were left in an environment with an ambient temperature of 60° C.and a relative humidity of 90%, and the time (hours) was recorded at thepoint when each optical filter whitened (became turbid) and devitrified(determined visually). The results are given in Table 1 (the components,etc., of the optical filters are also given in Table 1). It was foundfrom these results that there is a tendency for devitrification to beless likely to occur as the P/Cu molar ratio decreases.

Whereas the optical filters of the comparative examples underwentdevitrification at 660 hours at the longest, the optical filters of theexamples took at least 1100 hours to undergo devitrification. Thisconfirms that the optical filters of the present invention have muchbetter moisture resistance. Furthermore, the optical filter of Example3, which was produced by further adding water to the composition ofExample 2, took longer to reach devitrification than that of Example 2.This confirms the effectiveness of adding water during preparation.

TABLE 1 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex. 2 Ex. 3 P/Cu*11.13 1.20 1.20 1.42 1.71 1.71 Copper ion 6.1 6.1 6.1 3.9 6.1 3.9 content(wt %) Composition phosphoric 16 17.3 17.3 12 21.5 14.5 ester Aphosphoric 14.4 15 15 11.7 23.5 14 ester B diethylene 20 20 20 20 20 20glycol dimethacrylate methyl 48.6 46.7 46.7 55.3 34 50.5 methacrylate α-0.9 0.9 0.9 0.9 0.9 0.9 methylstyrene copper 32 32 32 20 32 20 benzoatetert-butyl 2 2 2 2 2 2 peroxy- octanoate Optical filter Thickness 0.50.5 0.5 0.5 0.5 0.5 (mm) Whitening 1824 1153 1526 660 137 166 time*2(hours) Notes *1: Given as the molar ratio. *2: Given as the time untilthe optical filter whitened and devitrified when a moisture resistancetest was conducted in an environment with an ambient temperature of 60°C. and a relative humidity of 90%.

INDUSTRIAL APPLICABILITY

As described above, with the present invention, when adequate nearinfrared light absorption is obtained by raising the copper ion contentwhen the thickness of a near infrared light absorption layer has beenreduced in an optical filter, a specific phosphoric ester compound isused, and the contents of phosphorus atoms and copper ions in the nearinfrared light absorption layer are set to specific values, namely, thephosphorus atom content is set to between 0.4 and 1.3 mol per mole ofcopper ions, which makes it possible to obtain an optical filter withextremely good moisture resistance while still having sufficient nearinfrared light absorption.

1. An optical filter, comprising a near infrared light absorption layercontaining the following component A and/or the following component B,wherein the phosphorus atom content in the near infrared lightabsorption layer is 0.4 to 1.3 mol per mole of copper ions, and thecopper ion content in the near infrared light absorption layer is 2 to60 wt %: Component A: a component composed of copper ions and aphosphoric ester compound expressed by the following Formula (1);Component B: a copper phosphate compound obtained by reaction of acopper compound with said phosphoric ester compound,

(in Formula (1), R is a group expressed by the following Formula (2),(3), (4), (5), (6), (7), (8), or (9), an alkyl group, an aryl group, anaralkyl group, or an alkenyl group, n is 1 or 2, and when n is 1, the Rgroups may be the same or different),

(in Formulas (2) to (9), R¹¹ to R¹⁷ are C₁ to C₂₀ alkyl groups or C₆ toC₂₀ aryl groups or aralkyl groups (where the one or more hydrogen atomsbonded to the carbon atoms that make up aromatic rings may besubstituted with C₁ to C₆ alkyl groups or halogens), R²¹ to R²⁵ arehydrogen atoms or C₁ to C₄ alkyl groups (where R²³, R²⁴, and R²⁵ cannotall be hydrogen atoms), R³¹ and R³² are C₁ to C₆ alkylene groups, R⁴¹ isa C₁ to C₁₀ alkylene group, R⁵¹ and R⁵² are C₁ to C₂₀ alkyl groups, R⁶¹is a hydrogen atom or methyl group, m is an integer from 1 to 6, k is aninteger from 0 to 5, p is an integer from 2 to 97, and r is an integerfrom 1 to 4).
 2. The optical filter according to claim 1, wherein thephosphorus atom content in the near infrared light absorption layer is0.8 to 1.3 mol per mole of copper ions.
 3. The optical filter accordingto claim 1, wherein the phosphoric ester compound is such that R⁶¹ inFormula (9) is a methyl group, p in Formula (9) is 2 or 3, and r inFormula (9) is
 1. 4. A method for manufacturing an optical filter havinga near infrared light absorption layer containing the followingcomponent A and/or the following component B: Component A: a componentcomposed of copper ions and a phosphoric ester compound expressed by thefollowing Formula (1);

Component B: a copper phosphate compound obtained by reaction of acopper compound with said phosphoric ester compound, comprising the stepof mixing or bringing into contact a phosphoric ester compound expressedby Formula (1), a copper salt, and water.
 5. The method formanufacturing an optical filter according to claim 4, said stepcomprising: mixing or bringing into contact a phosphoric ester compoundexpressed by Formula (1), a copper salt, and water such that thephosphorus atom content in the near infrared light absorption layer is0.4 to 1.3 mol per mole of copper ions, and the copper ion content inthe near infrared light absorption layer is 2 to 60 wt %.